Double-blown pet bottle shaped container having essentially no residual stress and superior heat resistance

ABSTRACT

A biaxially oriented polyethylene terephthalate resin bottle-shaped container, and method of blow-molding the same, is disclosed. The method comprises the steps of heating the body portion of a preform at 90° to 130° C., biaxial-orientation blow-molding the preform in a primary blowing mold heated at 110 to 230° C. to form a primary intermediate molded bottle-shaped piece, heating the primary intermediate molded bottle-shaped piece at 130 to 255° C. or at a temperature which is at least 20° C. greater than the primary blowing mold temperature to form a secondary intermediate molded bottle-shaped piece, and blow-molding the secondary intermediate molded bottle-shaped piece in a secondary blowing mold heated at 100° to 150° C. to form a bottle-shaped container. The temperature of the secondary blowing mold is several degrees greater than the maximum temperature the molded bottle-shaped container will be subjected to during use. The bottle-shaped container of the present invention has no stress remaining from biaxial orientation blow-molding and has a high heat resistance temperature value.

This application is a divisional of application Ser. No. 08/683,431,filed Jul. 18, 1996 now U.S. Pat. No. 5,747,130 and allowed Sep. 30,1997, which is a divisional of application Ser. No. 08/327,893 filedOct. 24, 1994, U.S. Pat. No. 5,562,960, which is a continuation ofapplication Ser. No. 08/076,095 filed Jun. 14, 1993, abandoned, which isa continuation of application Ser. No. 07/866,099 filed Apr. 6, 1992,U.S. Pat. No. 5,248,533, which is a continuation of application Ser. No.07/588,491 filed Sep. 6, 1990, abandoned, which in turn is acontinuation of application Ser. No. 07/171,101 filed Mar. 21, 1988,abandoned, which is a divisional of application Ser. No. 06/897,035filed Aug. 15, 1986, abandoned, which in turn is a continuation-in-partof application Ser. No. 06/701,352 filed Feb. 13, 1985, abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a method of blow-molding abiaxially-oriented polyethylene terephthalate resin bottle-shapedcontainer, and the biaxially-oriented polyethylene terephthalate resinbottle-shaped container made according to said method.

Polyethylene terephthalate resin (hereinafter referred to as "PET") hasstable physical properties, excellent transparency and high mechanicalstrength. Also, PET causes no pollution when incinerated. PET is widelyused in the production of biaxially-oriented blow-molded bottle-shapedcontainers, and is particularly useful for bottling foodstuffs.

PET bottle-shaped containers have a number of excellent properties asdescribed above, however, blow-molded bottle-shaped containers ofbiaxially-oriented PET which are not heat treated suffer remarkabledeformation at temperatures of 70° C. or more. Therefore, such PETbottle-shaped containers cannot be used to bottle retort food, which isheat treated by allowing the food to stand for 30 min. at 120° C., orother heat treated food. Accordingly, there is great demand for PETbottle-shaped containers which have high heat resistance.

There are several conventional methods of imparting heat resistance toPET bottle-shaped containers such as (1) heating a blowing mold duringblow-molding of a PET bottle-shaped container to a temperature higherthan the target heat resistance temperature value to increase thedensity of the PET bottle-shaped container; (2) heat setting a PETbottle-shaped container after biow-molding to remove residual strainproduced by blow-molding; and (3) blow-molding an intermediate moldedpiece by first molding a primary blow-molded container, then reheatingit at approximately 110° C., and finally blowing it again to produce abottle-shaped container.

In method (1), the moldability of the PET decreases as the moldtemperature rises. According to this method, the PET is heat resistantup to a maximum of approximately 100° C. This PET cannot be used forbottle-shaped containers containing food which is heat treated attemperatures much higher than 100° C. Methods (2) and (3) of impartingheat resistance to a PET bottle-shaped container cannot expect toproduce a heat resistance higher than that of method (1).

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide abiaxially-oriented PET bottle-shaped container, and a method ofblow-molding the same, which can eliminate the afore-mentioned drawbacksand disadvantages of the conventional methods.

It is another object of the present invention to provide abiaxially-oriented PET bottle-shaped container having very high heatresistance, and a method of blow-molding the same. This object isaccomplished by a method in which a preform is biaxial-orientationblow-molded to form a primary intermediate molded piece, the primaryintermediate molded piece is heat treated to thermally contract anddeform the piece to form a secondary intermediate molded piece and thenthe secondary intermediate molded piece is blow-molded to form a finalbottle-shaped container.

The foregoing objects and other objects, as well as the characteristicfeatures of the invention will become more fully apparent and morereadily understandable from the following description and the appendedclaims when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view depicting the primaryblow-molding state of a primary intermediate molded piece according tothe present invention;

FIG. 2 is a longitudinal sectional view showing the secondaryblow-molding state of a secondary intermediate molded piece according tothe present invention; and

FIG. 3 is a graphic diagram showing the relationship between the densityand the blow-molding temperature of the blow-molded bottle-shapedcontainer of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described in detailwith reference to the accompanying drawings.

With reference to FIG. 1, the method of blow-molding thebiaxially-oriented PET bottle-shaped container according to the presentinvention comprises the steps of: heating the body portion 2 of apreform 1, which is formed in a desired shape in advance, at 90° C. to130° C. (preferably 100° C. to 120° C.) until the temperature approachesbut does not reach the thermal crystallization temperature of the PET,biaxial-orientation blow-molding the preform in a primary blowing moldheated at 110° C. to 230° C. (preferably 140° C. to 230° C. ) to form aprimary intermediate molded bottle-shaped piece 4, heating the primaryintermediate molded bottle-shaped piece 4 at 130° C. to 255° C.(preferably 170° C. to 255° C. or more preferably 200° C. to 235° C.)which is in a range that does not exceed the temperature immediatelybefore the melting point at 255° C. of polyethylene terephthalate, or ata temperature which is at least 20° C. greater than the primary blowingmold temperature to form a secondary intermediate molded bottle-shapedpiece 5 (FIG. 2), and blow-molding the secondary intermediate moldedbottle-shaped piece 5 in a secondary blowing mold heated at 100° C. to150° C. (preferably 120° C. to 150° C.), which is higher than thesterilizing temperature of the contents filled in the moldedbottle-shaped container, to form a final bottle-shaped container 6.

More particularly, the method of blow-molding the biaxially-oriented PETbottle-shaped container of the present invention includes a first stepof injection molding, in advance, a preform I in a desired shaped, asecond step of thermally crystallizing, without orienting deformation, aneck portion of the bottle-shaped container 6 which remains in the sameshape as at the injection molding time, and a third step of blow-moldingthe body of the bottle-shaped container 6.

The preform 1 is injection molded by ordinary injection moldingtechniques. In the exemplified embodiment, the injection molded preform1 is formed in a dish shape as shown by solid lines in FIG. 1. Thepreform 1 has a neck portion 3 and a body portion 2. The body portion 2becomes the body, including a bottom, of the biaxially-orientedblow-molded bottle-shaped container 6.

The body 2 is orientation magnified 5 to 13 times so that the orientingdensity may become 1.36 or more and so that the body 2 is not thermallycrystallized even with a primary blowing mold temperature of 110° C. to230° C. at the blow-molding time.

Thus, the body 2 is formed in the primary intermediate molded piece 4without thermal crystallization even at the primary blowing moldtemperature of 110° C. to 230° C. which is higher than the crystallizingtemperature of the PET.

The peripheral end of a connecting portion between the body portion 2and the neck portion 3 and the central portion of the body portion arehardly oriented as compared with other parts of the body portion 2 andare also readily crystallized. These portions are therefore preferablyreduced in thickness relative to the other parts of the body portion 2so as to be readily oriented.

The neck portion 3 of the preform 1 is, preferably, thermallycrystallized or whitened prior to biaxial-orientation blow-molding thepreform to form the primary intermediate molded bottle-shaped piece 4.The whitening of the neck portion 3 may be performed by sufficientlyheating the neck portion 3 to crystallize the PET, followed by gradualcooling. It should be noted, however, that all deformation of the neckportion 3 should be avoided when whitening the neck portion 3.Particularly, deterioration of the degree of the circularity of the neckportion 3 should be avoided since such deformation would largely reducethe function of the final blow-molded bottle-shaped container 6.

After the neck portion 3 of the preform 1 is whitened in this manner,the preform 1 is blow-molded to form the bottle-shaped container 6. Theblow-molding step involves biaxial-orientation blow-molding the preform1 to form a primary intermediate molded bottle-shaped piece 4, heatingthe primary intermediate molded bottle-shaped piece 4 to thermallyshrink it and form a secondary intermediate molded bottle-shaped piece5, and blow-molding the secondary intermediate molded bottle-shapedpiece 5 to form a final bottle-shaped container 6.

The step of biaxial-orientation blow-molding the preform 1 to form theprimary intermediate molded bottle-shaped piece 4 is performed by firstheating the body portion 2 of the preform 1 at 90° C. to 130° C.(preferably 100° C. to 120° C.) until the temperature approaches butdoes not reach the thermal crystallization temperature of the PET.

Next, the preform 1 is blow-molded in a blowing mold heated at 110° C.to 230° C. to form the primary intermediate bottle-shaped piece 4. Theprimary intermediate molded bottle-shaped piece 4 is oriented so thatthe area magnification of the preform 1 to the primary intermediatemolded bottle-shaped piece 4 is in a range of 5 to 13 times and so thatthe density of the resin becomes 1.36 or more to prevent thebottle-shaped piece 4 from being thermally crystallized by the heatingtemperature of the primary mold and the heating temperature of thesecondary intermediate molded piece.

The primary intermediate molded bottle-shaped piece 4 is then heated tothermally shrink it to form the secondary intermediate moldedbottle-shaped piece 5. This shrinking step is performed to permitthermal deformation by eliminating residual stress developed in theblow-molded piece 4 from biaxial-orientation blow-molding. Theorientation blow-molded portion of the primary intermediate moldedbottle-shaped piece 4 is deformed by the internal residual stress byheating the primary intermediate molded bottle-shaped piece 4 in afurnace at 130° C. to 255° C. or a temperature which is at least 20° C.greater than the primary blowing mold temperature, (preferably 170° C.to 255° C. or more preferably 200° C. to 235° C.), to eliminate theresidual stress. The deformation produced by the elimination of theinternal residual stress acts to contract or shrink theorientation-molded portion of the primary intermediate moldedbottle-shaped piece 4. Consequently, the orientation-molded portion ofthe secondary intermediate molded bottle-shaped piece 5 is molded bythis contraction deformation.

The body portion of the secondary intermediate molded bottle-shapedpiece 5 formed by the shrinkage deformation is predetermined in theorienting magnification from the preform 1 to the primary intermediatemolded piece 4 and from the size of the primary intermediate moldedpiece 4 to be substantially equal to or slightly smaller than theorientation-molded body portion of the final bottle-shaped container 6as shown in FIG. 2.

Finally, the secondary intermediate molded bottle-shaped piece 5 isblow-molded to form the final bottle-shaped container 6. The secondaryintermediate molded bottle-shaped piece 5 is thermally shrunk by heatingat 130° C. to 255° C. or at a temperature which is at least 20° C.greater than the primary blowing mold temperature (preferably 170°C.-255° C. or more preferably, 200° C. -235° C.) as described above, andis placed in the secondary blowing mold which is heated at a temperatureof 100° C. to 150° C. (preferably 120° C. to 150° C.). The temperatureof the secondary blowing mold is several degrees greater than themaximum temperature the molded bottle-shaped container 6 will besubjected to during use.

The body shape of the blow-molded portion of the secondary intermediatemolded bottle-shaped piece 5 is substantially equal to or slightlysmaller than the corresponding body shape of the bottle-shaped container6 as described above. Accordingly, the orientation magnification fromthe secondary intermediate molded bottle-shaped piece 5 to the finalbottle-shaped container 6 is quite small, and consequently almost nostress is created when the bottle-shaped container 6 molded from thesecondary intermediate molded bottle-shaped piece 5 isorientation-molded.

Further, since the bottle-shaped container 6 is blow-molded by asecondary blowing mold heated at a temperature greater than thetemperature the bottle-shaped container will be subjected to during use,the bottle-shaped container 6 is heatset by the secondary blowing mold,and therefore the bottle-shaped container 6 has no residual stress aswell as high heat resistance.

FIG. 3 shows the relationship between the density of the moldingmaterial at the respective molding steps and the mold temperatures.

A specific example of the method of blow-molding the biaxially-orientedPET bottle-shaped container of the present invention will now bedescribed.

A preform 1 was biaxial-orientation blow-molded to form a primaryintermediate molded bottle-shaped piece 4. The preform was heated to atemperature of 115° C. and was blow-molded at a primary blowing moldtemperature of 180° C. under a blowing pressure of 25 kg/cm² for ablowing time of 1.4 sec. The primary intermediate molded bottle-shapedpiece 4 was then heated and thermally shrunk to form a secondaryintermediate molded bottle-shaped piece 5 at a heating temperature of225° C. The secondary intermediate molded bottle-shaped piece 5 wasblow-molded at a secondary blowing mold temperature of 140° C. under ablowing pressure of 30 kg/cm² for a blowing time of 4.4 sec. to form thefinal blow-molded bottle-shaped container 6.

The heat resistance of the blow-molded bottle-shaped container 6 wasthen tested by immersing it without a cap for 30 minutes in a tank ofglycerin heated at 120° C. The bottle-shaped container 6 was thenremoved from the glycerin and water-cooled. The volumetric variation ofthe container before heating and after heating was measured. Thevolumetric rate of change of the bottle-shaped container 6 was found tobe 0.33%. From this result, it is apparent that a PET bottle-shapedcontainer having sufficiently high heat resistance can be provided bythe present invention.

According to the method of the present invention as described above, themethod of blow-molding the PET bottle-shaped container provides theblow-molded bottle-shaped container of the present invention which hasno residual stress and extremely high heat resistance. The heatresistance temperature value is remarkably increased when compared withthat of a conventional container.

While the present invention has been described in detail and withreference to specific examples thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madewithout departing from the spirit and scope thereof.

What is claimed is:
 1. A blow-molded biaxially oriented polyethyleneterephthalate resin bottle-shaped container made by the following methodto have substantially no residual stress and to have high heatresistance, the method comprising the steps of:providing a preform witha neck and a body; first biaxial-orientation blow-molding the preform ina first mold at a first temperature to biaxially stretch the preform toform a primary intermediate molded bottle-shaped piece that is largerthan the bottle-shaped container, the primary intermediate moldedbottle-shaped piece having residual stress created by the biaxialstretching; causing thermal contraction of the primary intermediatemolded bottle-shaped piece at a temperature higher than the firsttemperature to form a secondary intermediate molded bottle-shaped piece,the secondary intermediate molded bottle-shaped piece having at leastone of a height, a diameter and a volume that is substantially equal toor smaller than that of the bottle-shaped container and having residualstress caused by the first blow-molding eliminated by the thermalcontraction; and second blow-molding the secondary intermediate moldedbottle-shaped piece in a second mold to form the bottle-shapedcontainer, wherein the secondary intermediate molded bottle-shaped piecehas a small orientation magnification and substantially no stress iscreated during the second blow-molding, and wherein said bottle-shapedcontainer formed exhibits essentially no residual stress and alsoexhibits essentially no shrinkage or deformation when said containercontains contents having a temperature of 120° C., and wherein theformation of said primary and secondary pieces results in saiddouble-blown container being capable of containing contents heat treatedat temperatures up to 120° C. with essentially no container deformationor shrinkage.
 2. The container of claim 1, wherein said step ofproviding the preform includes forming the preform.
 3. The container ofclaim 1, wherein said step of providing the preform includes thermallycrystallizing the neck of the preform.
 4. The container of claim 1,wherein said step of first biaxial-orientation blow-molding the preformincludes biaxially stretching the preform to result in the primaryintermediate molded bottle-shaped piece with an area magnification of 5to 13 times the preform.
 5. The container of claim 1, wherein said stepof first biaxial-orientation blow-molding the preform includes biaxiallystretching the preform to result in the primary intermediate moldedbottle-shaped piece having a density of 1.36 gm/cc or more.
 6. Thecontainer of claim 1, wherein said step of first biaxial-orientationblow-molding the preform includes heating the body of the preform at atemperature in the range of 90° C. to 130° C. and blow-molding theheated preform in a blowing mold heated to a temperature in the range of110° C. to 230° C.
 7. The container of claim 6, wherein said step ofheating the body of the preform includes heating the preform at atemperature in the range of 100° C. to 120° C.
 8. The container of claim1, wherein said step of causing thermal contraction includes heating theprimary intermediate molded bottle-shaped piece in the first mold. 9.The container of claim 1, wherein said step of causing thermalcontraction includes heating the primary intermediate moldedbottle-shaped piece at a temperature in the range of 130° C. to 255° C.10. The container of claim 1, wherein said step of causing thermalcontraction includes heating the primary intermediate moldedbottle-shaped piece at a temperature in the range of 170° C. to 255° C.11. The container of claim 1, wherein said step of causing thermalcontraction includes heating the primary intermediate moldedbottle-shaped piece at a temperature in the range of 200° C. to 235° C.12. The container of claim 1, wherein said step of second blow-moldingthe secondary intermediate molded bottle-shaped piece includes placingthe secondary intermediate molded bottle-shaped piece in a second moldheated to a temperature in the range of 100° C. to 150° C. andblow-molding the secondary intermediate molded bottle-shaped piece toform the bottle-shaped container.
 13. The container of claim 12, whereinsaid step of second blow-molding the secondary intermediate moldedbottle-shaped piece includes heat treating the bottle-shaped containerby contacting the blow-molded bottle-shaped container with the secondmold heated to a temperature several degrees higher than a maximum usetemperature for the bottle-shaped container.
 14. The container of claim1, wherein said step of second blow-molding the secondary intermediatemolded bottle-shaped piece includes placing the secondary intermediatemolded bottle-shaped piece in a second mold heated to a temperature inthe range of 120° C. to 150° C. and blow-molding the secondaryintermediate molded bottle-shaped piece to form the bottle-shapedcontainer.
 15. A blow-molded biaxially oriented polyethyleneterephthalate resin bottle-shaped container made by the following methodto have substantially no residual stress and to have high heatresistance, the method comprising the steps of:providing a preform witha neck and a body; first biaxial-orientation blow-molding the preform ina first mold at a first temperature to biaxially stretch the perform toform a primary intermediate molded bottle-shaped piece that is largerthan the bottle-shaped container and having an area magnification of atleast 5 times the preform, the primary intermediate molded bottle-shapedpiece having residual stress created by the biaxial stretching; causingthermal contraction of the primary intermediate molded bottle-shapedpiece at a temperature higher than the first temperature to form asecondary intermediate molded bottle-shaped piece that has at least oneof a height, a diameter and a volume that is substantially equal to orsmaller than that of the bottle-shaped container to eliminate residualstress caused by the first blow-molding; an second blow-molding thesecondary intermediate molded bottle-shaped piece in a second mold toform the bottle-shaped container, wherein said bottle-shaped containerformed exhibits essentially no residual stress and also exhibitsessentially no shrinkage or deformation when said container containscontents having a temperature of 120° C., and wherein the formation ofsaid primary and secondary pieces results in said double-blown containerbeing capable of containing contents heat treated at temperatures up to120° C. with essentially no container deformation or shrinkage.
 16. Thecontainer of claim 15, wherein said step of causing thermal contractionof the primary intermediate molded bottle-shaped piece includes heatingthe primary intermediate molded bottle-shaped piece at a temperature inthe range of 130° C. to 255° C.
 17. The container of claim 15, whereinsaid step of causing thermal contraction of the primary intermediatemolded bottle-shaped piece includes heating the primary intermediatemolded bottle-shaped piece at a temperature in the range of 170° C. to255° C.
 18. The container of claim 17, wherein said step of causingthermal contraction of the primary intermediate molded bottle-shapedpiece includes heating the primary intermediate molded bottle-shapedpiece at a temperature in the range of 200° C. to 235° C.
 19. Thecontainer of claim 15, wherein said step of providing the preformincludes thermally crystallizing the neck of the preform.
 20. Thecontainer of claim 15, wherein said step of first biaxial-orientationblow-molding the preform includes biaxially stretching the preform toresult in the primary intermediate molded bottle-shaped piece having adensity of 1.36 gm/cc or more.
 21. The container of claim 15, whereinsaid step of first biaxial-orientation blow-molding the preform includesheating the body of the preform at a temperature in the range of 90° C.to 130° C. and blow-molding the heated preform in a blowing mold heatedto a temperature in the range of 110° C. to 230° C.
 22. The container ofclaim 21, wherein said step of heating the body of the preform includesheating the preform at a temperature in the range of 100° C. to 120° C.23. The container of claim 15, wherein said step of second blow-moldingthe secondary intermediate molded bottle-shaped piece includes placingthe secondary intermediate molded bottle-shaped piece in a second moldheated to a temperature in the range of 100° C. to 150° C. andblow-molding the secondary intermediate molded bottle-shaped piece toform the bottle-shaped container.
 24. The container of claim 23, whereinsaid step of second blow-molding the secondary intermediate moldedbottle-shaped piece includes heat treating the bottle-shaped containerby contacting the blow-molded bottle-shaped container with the secondmold heated to a temperature several degrees higher than a maximum usetemperature for the bottle-shaped container.
 25. The container of claim15, wherein said step of second blow-molding the secondary intermediatemolded bottle-shaped piece includes placing the secondary intermediatemolded bottle-shaped piece in a second mold heated to a temperature inthe range of 120° C. to 150° C. and blow-molding the secondaryintermediate molded bottle-shaped piece to form the bottle-shapedcontainer.
 26. The bottle-shaped container of claim 15, wherein theprimary intermediate molded bottle-shaped piece has an areamagnification of 5 to 13 times the preform.
 27. A blow-molded biaxiallyoriented polyethylene terephthalate resin bottle-shaped container madeby the following method to have substantially no residual stress and tohave high heat resistance, the method comprising the steps of:providinga preform with a neck and a body; first biaxial-orientation blow-moldingthe preform in a first mold at a first temperature to biaxially stretchthe preform to form a primary intermediate molded bottle-shaped piecethat is larger than the bottle-shaped container, the biaxial stretchingcreating residual stress in the primary intermediate moldedbottle-shaped piece; causing thermal contraction of the primaryintermediate molded bottle-shaped piece at a temperature higher than thefirst temperature in the range of 200° C. to 255° C. to form a secondaryintermediate molded bottle-shaped piece that has at least one of aheight, a diameter and a volume that is substantially equal to orsmaller than that of the bottle-shaped container to eliminate residualstress caused by the first blow-molding; and second blow-molding thesecondary intermediate molded bottle-shaped piece in a second mold toform the bottle-shaped container, wherein said bottle-shaped containerformed exhibits essentially no residual stress and also exhibitsessentially no shrinkage or deformation when said container containscontents having a temperature of 120° C., and wherein the formation ofsaid primary and secondary pieces results in said double-blown containerbeing capable of containing contents heat treated at temperatures up to120° C. with essentially no container deformation or shrinkage.
 28. Thecontainer of claim 27, wherein said step of providing the preformincludes thermally crystallizing the neck of the preform.
 29. Thecontainer of claim 27, wherein said step of first biaxial-orientationblow-molding the preform includes biaxially stretching the preform toresult in the primary intermediate molded bottle-shaped piece having anarea magnification of 5 to 13 times the preform.
 30. The container ofclaim 27, wherein said step of first biaxial-orientation blow-moldingthe preform includes biaxially stretching the preform to result in theprimary intermediate molded bottle-shaped piece having a density of 1.36gm/cc or more.
 31. The container of claim 27, wherein said step of firstbiaxial-orientation blow-molding the preform includes heating the bodyof the preform and blow-molding the heated preform in a blowing moldheated to a temperature in the range of 110° C. to 230° C.
 32. Thecontainer of claim 31, wherein said step of heating the body of thepreform includes heating the preform at a temperature in the range of100° C. to 120° C.
 33. The container of claim 27, wherein said step ofsecond blow-molding the secondary intermediate molded bottle-shapedpiece includes placing the secondary intermediate molded bottle-shapedpiece in a second mold heated to a temperature in the range of 100° C.to 150° C. and blow-molding the secondary intermediate moldedbottle-shaped piece to form the bottle-shaped container.
 34. Thecontainer of claim 33, wherein said step of second blow-molding thesecondary intermediate molded bottle-shaped piece includes heat treatingthe bottle-shaped container by contacting the blow-molded bottle-shapedcontainer with the second mold heated to a temperature several degreeshigher than a maximum use temperature for the bottle-shaped container.35. The container of claim 27, wherein said step of second blow-moldingthe secondary intermediate molded bottle-shaped piece includes placingthe secondary intermediate molded bottle-shaped piece in a second moldheated to a temperature in the range of 120° C. to 150° C. andblow-molding the secondary intermediate molded bottle-shaped piece toform the bottle-shaped container.
 36. A blow-molded biaxially orientedpolyethylene terephthalate resin bottle-shaped container, formed by thefollowing method to have high heat resistance, the method comprising thesteps of:a) forming a preform having a preliminary shape including aneck and a body; b) first biaxial-orientation blow-molding the preformin a first mold to form a primary intermediate molded bottle-shapedpiece, wherein the primary intermediate molded bottle-shaped piece hasan area magnification from the preform in the range of 5 to 13 times anda density of 1.36 gm/cc or more, by the steps of(i) heating the body ofthe preform to a temperature that approaches but does not reach athermal crystallization temperature of polyethylene terephthalate resin,and (ii) blow-molding the preform in a blow-mold heated to a temperaturein the range of 110° C. to 230° C. to form a primary intermediate moldedbottle-shaped piece that is larger than the bottle-shaped container; c)causing thermal contraction of the primary intermediate moldedbottle-shaped piece to form a secondary intermediate moldedbottle-shaped piece to eliminate residual stress in the primaryintermediate molded bottle-shaped piece resulting from the first blow,wherein the secondary intermediate molded bottle-shaped piece has atleast one of a height, a diameter and a volume that is substantiallyequal to or smaller than that of the bottle-shaped container, by thestep of heating the primary intermediate molded bottle-shaped piece to atemperature of at least 20° C. greater than the temperature of the moldof the first step of blow-molding; and d) second blow-molding thesecondary intermediate molded bottle-shaped piece in a second mold toform the bottle-shaped container having a small orientationmagnification from the secondary intermediate molded bottle-shapedpiece, wherein substantially no stress is created when the bottle-shapedcontainer is blow-molded, by the steps of(i) placing the secondaryintermediate molded bottle-shaped piece in a mold heated to atemperature in the range of 100° C. to 150° C., and (ii) blow-moldingthe secondary intermediate molded bottle-shaped piece to form thebottle-shaped container, wherein said bottle-shaped container formedexhibits essentially no residual stress and also exhibits essentially noshrinkage or deformation when said container contains contents having atemperature of 120° C. and wherein the formation of said primary andsecond pieces results in said double-blown container being capable ofcontaining contents heat treated at temperatures up to 120° C. withessentially no container deformation or shrinkage.
 37. The container ofclaim 36, wherein said step of forming a preform includes heating thepreform to a temperature in a range of 100° C. to 120° C.
 38. Thecontainer of claim 36, wherein the step of first biaxial-orientationblow-molding the preform to form a primary intermediate moldedbottle-shaped piece includes blow-molding the preform in a blow-moldheated to a temperature in the range of 140° C. to 230° C.
 39. Thecontainer of claim 36, wherein the step of molding the primaryintermediate molded bottle-shaped piece by contraction deformation toform a secondary intermediate molded bottle-shaped piece includesheating the primary intermediate molded bottle-shaped piece to atemperature in the range of 130° C. to 255° C.
 40. The container ofclaim 36, wherein the step of causing thermal contraction of the primaryintermediate molded bottle-shaped piece to form a secondary intermediatemolded bottle-shaped piece includes heating the primary intermediatemolded bottle-shaped piece to a temperature in the range of 170° C. to255° C.
 41. The container of claim 36, wherein the step of causingthermal contraction of the primary intermediate molded bottle-shapedpiece to form a secondary intermediate molded bottle-shaped pieceincludes heating the primary intermediate molded bottle-shaped piece toa temperature in the range of 200° C. to 235° C.
 42. The container ofclaim 36, wherein the step of second blow-molding the secondaryintermediate molded bottle-shaped piece to form the bottle-shapedcontainer includes placing the molded secondary intermediate moldedbottle-shaped piece in a mold heated to a temperature in the range of120° C. to 150° C.
 43. The container of claim 36, including the step ofthermally crystallizing the neck of the preform.
 44. A blow-moldedbiaxially oriented polyethylene terephthalate resin bottle-shapedcontainer, formed by the following method to have high heat resistance,the method comprising the steps of:biaxial-orientation blow molding apreform in a first mold to biaxially stretch the perform to form aprimary intermediate molded bottle-shaped piece that is larger than thebottle-shaped container; and forming the bottle-shaped container fromthe primary intermediate molded bottle-shaped piece; wherein the primaryintermediate molded bottle-shaped piece is heated to be forciblythermally contracted to form a secondary intermediate moldedbottle-shaped piece that has at least one of a height, a diameter and avolume that is substantially equal to or smaller than that of thebottle-shaped container; and further wherein the secondary intermediatemolded bottle-shaped piece is blow molded in a second mold to form thebottle-shaped container, wherein said bottle-shaped container formedexhibits essentially no residual stress and also exhibits essentially noshrinkage or deformation when said container contains contents having atemperature of 120° C. and wherein the formation of said primary andsecondary pieces results in said double-blown container being capable ofcontaining contents heat treated at temperatures up to 120° C. withessentially no container deformation or shrinkage.
 45. A blow-moldedbiaxially oriented polyethylene terephthalate resin bottle-shapedcontainer, formed by the following method to have high heat resistance,the method comprising the steps of:heating a preform at a temperaturethat approaches but does not reach the thermal crystallizationtemperature of the polyethylene terephthalate resin; biaxial-orientationblow molding the preform in a primary blow mold at a primary blow moldtemperature to biaxially stretch the preform to form a primaryintermediate molded bottle-shaped piece that is larger than thebottle-shaped container; and forming the bottle-shaped container fromthe primary intermediate molded bottle-shaped piece; wherein the primaryintermediate molded bottle-shaped piece is heated to a temperaturehigher than the primary blow mold temperature to thermally shrink andeliminate residual stress from the primary intermediate bottle-shapedpiece to form a secondary intermediate molded bottle-shaped piece thathas at least one of a height, a diameter and a volume that issubstantially equal to or smaller than that of the bottle-shapedcontainer; and further wherein the secondary intermediate moldedbottle-shaped piece is blow molded in a secondary blow mold to form thebottle-shaped container, wherein said bottle-shaped container formedexhibits essentially no residual stress and also exhibits essentially noshrinkage or deformation when said container contains contents having atemperature of 120° C. and wherein the formation of said primary andsecondary pieces results in said double-blown container being capable ofcontaining contents heat treated at temperatures up to 120° C. withessentially no container deformation or shrinkage.
 46. A double-blownbiaxially oriented polyethylene terephthalate resin molded bottle-shapedcontainer, said double-blown container being formed from a preforminitially heated, primarily biaxial orientation blow molded and shapedto form a primary intermediate shaped container, said primaryintermediate shaped container being heated and reshaped to form asecondary intermediate shaped container that has at least one of aheight, a diameter and a volume that is substantially equal to orsmaller than that of the bottle-shaped container, said secondaryintermediate shaped container being secondarily blown and reshaped toform said double-blown container, said primary and second intermediateshaped containers comprising means for providing said double-blowncontainer with essentially no residual stress, wherein the double-blowncontainer exhibits essentially no shrinkage or deformation when saiddouble-blown container contains contents heated to a temperature of 120°C., said double-blown container capable of containing contents heattreated at temperatures up to 120° C. with essentially no deformation orshrinkage.
 47. A double-blown container according to claim 46, whereinsaid double-blown container has a shape including a neck portion, abottom portion and a body that connects the neck portion and the bottomportion, said body being substantially transparent and non-whitened. 48.A double-blown container according to claim 46, wherein saiddouble-blown container includes a body portion having an orientationmagnification of about 5 to
 13. 49. A double-blown container accordingto claim 46, wherein said double-blown container exhibits a volumetricrate of change of no greater than 0.33 percent when exposed totemperatures substantially in said temperature range.
 50. A double-blownbiaxially oriented polyethylene terephthalate resin molded bottle-shapedcontainer used to contain heated contents therein, said double-blowncontainer being formed from a preform initially heated, primarilybiaxial orientation blow molded and shaped to form a primaryintermediate shaped container, said primary intermediate shapedcontainer being heated and reshaped to form a secondary intermediateshaped container, said secondary intermediate shaped container beingsecondarily blown and reshaped to form said double-blown container, saiddouble-blown container having essentially no residual stress andexhibiting a volumetric rate of change of 0.33 percent or less whenexposed to heated contents having a temperature of 120° C. to avoiddeformation and shrinkage of the double-blown container when said heatedcontents contained within said double-blown container have been heatsterilized at temperatures up to about 120° C.
 51. A double-blowncontainer according to claim 50, wherein said heat sterilization rangeis about 70° C. to 120° C.
 52. A double-blown container according toclaim 50, wherein said double-blown container has a shape including aneck portion, a bottom portion and a body that connects the neck portionand the bottom portion, said body being transparent and non-whitened.53. A double-blown container according to claim 50, wherein saiddouble-blown container includes a body portion having an orientationmagnification of about 5 to 13.